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361.
Pedulla ML Ford ME Karthikeyan T Houtz JM Hendrix RW Hatfull GF Poteete AR Gilcrease EB Winn-Stapley DA Casjens SR 《Journal of bacteriology》2003,185(4):1475-1477
We report the first accurate genome sequence for bacteriophage P22, correcting a 0.14% error rate in previously determined sequences. DNA sequencing technology is now good enough that genomes of important model systems like P22 can be sequenced with essentially 100% accuracy with minimal investment of time and resources. 相似文献
362.
Photosynthesis of cotton plants exposed to elevated levels of carbon dioxide in the field 总被引:14,自引:0,他引:14
John W. Radin Bruce A. Kimball Donald L. Hendrix Jack R. Mauney 《Photosynthesis research》1987,12(3):191-203
The cotton (Gossypium hirsutum L.) plant responds to a doubling of atmospheric CO2 with almost doubled yield. Gas exchange of leaves was monitored to discover the photosynthetic basis of this large response. Plants were grown in the field in open-top chambers with ambient (nominally 350 l/l) or enriched (nominally either 500 or 650 l/l) concentrations of atmospheric CO2. During most of the season, in fully-irrigated plants the relationship between assimilation (A) and intercellular CO2 concentration (ci) was almost linear over an extremely wide range of ci. CO2 enrichment did not alter this relationship or diminish photosynthetic capacity (despite accumulation of starch to very high levels) until very late in the season, when temperature was somewhat lower than at midseason. Stomatal conductance at midseason was very high and insensitive to CO2, leading to estimates of ci above 85% of atmospheric CO2 concentration in both ambient and enriched chambers. Water stress caused A to show a saturation response with respect to ci, and it increased stomatal closure in response to CO2 enrichment. In fully-irrigated plants CO2 enrichment to 650 l/l increased A more than 70%, but in water-stressed plants enrichment increased A only about 52%. The non-saturating response of A to ci, the failure of CO2 enrichment to decrease photosynthetic capacity for most of the season, and the ability of the leaves to maintain very high ci, form in part the basis for the very large response to CO2 enrichment.Abbreviations ca-
atmospheric CO2 concentration
- ci-
intercellular CO2 concentration
- A-
rate of assimilation of CO2
- gs-
stomatal conductance to water vapor
- gb-
boundary layer conductance to water vapor
- gm-
mesophyll conductance to CO2
- VPD-
vapor pressure deficit
- w
leaf water potential
- L-
stomatal limitation to CO2 uptake 相似文献
363.
Crosslinking renders bacteriophage HK97 capsid maturation irreversible and effects an essential stabilization 下载免费PDF全文
Ross PD Cheng N Conway JF Firek BA Hendrix RW Duda RL Steven AC 《The EMBO journal》2005,24(7):1352-1363
In HK97 capsid maturation, structural change ('expansion') is accompanied by formation of covalent crosslinks, connecting residue K169 in the 'E-loop' of each subunit with N356 on another subunit. We show by complementation experiments with the K169Y mutant, which cannot crosslink, that crosslinking is an essential function. The precursor Prohead-II passes through three expansion intermediate (EI) states en route to the end state, Head-II. We investigated the effects of expansion and crosslinking on stability by differential scanning calorimetry of wild-type and K169Y capsids. After expansion, the denaturation temperature (Tp) of K169Y capsids is slightly reduced, indicating that their thermal stability is not enhanced, but crosslinking effects a major stabilization (deltaTp, +11 degrees C). EI-II is the earliest capsid to form crosslinks. Cryo-electron microscopy shows that for both wild-type and K169Y EI-II, most E-loops are in the 'up' position, 30 A from the nearest N356: thus, crosslinking in EI-II represents capture of mobile E-loops in 'down' positions. At pH 4, most K169Y capsids remain as EI-II, whereas wild-type capsids proceed to EI-III, suggesting that crosslink formation drives maturation by a Brownian ratchet mechanism. 相似文献
364.
Rojas JD Sennoune SR Martinez GM Bakunts K Meininger CJ Wu G Wesson DE Seftor EA Hendrix MJ Martínez-Zaguilán R 《Journal of cellular physiology》2004,201(2):190-200
Angiogenesis requires invasion of extracellular matrix (ECM) proteins by endothelial cells and occurs in hypoxic and acidic environments that are not conducive for cell growth and survival. We hypothesize that angiogenic cells must exhibit a unique system to regulate their cytosolic pH in order to cope with these harsh conditions. The plasmalemmal vacuolar type H(+)-ATPase (pmV-ATPase) is used by cells exhibiting an invasive phenotype. Because angiogenesis is impaired in diabetes, we hypothesized that pmV-ATPase is decreased in microvascular endothelial cells from diabetic rats. The in vitro angiogenesis assays demonstrated that endothelial cells were unable to form capillary-like structures in diabetes. The proton fluxes were slower in cells from diabetic than normal model, regardless of the presence or absence of Na(+) and HCO(3) (-) and were suppressed by V-H(+)-ATPase inhibitors. Immunocytochemical data revealed that pmV-ATPases were inconspicuous at the plasma membrane of cells from diabetic whereas in normal cells were prominent. The pmV-ATPase activity was lower in cells from diabetic than normal models. Inhibition of V-H(+)-ATPase suppresses invasion/migration of normal cells, but have minor effects in cells from diabetic models. These novel observations suggest that the angiogenic abnormalities in diabetes involve a decrease in pmV-ATPase in microvascular endothelial cells. 相似文献
365.
Klosterman PS Hendrix DK Tamura M Holbrook SR Brenner SE 《Nucleic acids research》2004,32(8):2342-2352
Release 2.0.1 of the Structural Classification of RNA (SCOR) database, http://scor.lbl.gov, contains a classification of the internal and hairpin loops in a comprehensive collection of 497 NMR and X-ray RNA structures. This report discusses findings of the classification that have not been reported previously. The SCOR database contains multiple examples of a newly described RNA motif, the extruded helical single strand. Internal loop base triples are classified in SCOR according to their three-dimensional context. These internal loop triples contain several examples of a frequently found motif, the minor groove AGC triple. SCOR also presents the predominant and alternate conformations of hairpin loops, as shown in the most well represented tetraloops, with consensus sequences GNRA, UNCG and ANYA. The ubiquity of the GNRA hairpin turn motif is illustrated by its presence in complex internal loops. 相似文献
366.
Wang J Froeyen M Hendrix C Andrei C Snoeck R Lescrinier E De Clercq E Herdewijn P 《Nucleosides, nucleotides & nucleic acids》2001,20(4-7):727-730
(D)- and (L)-cyclohexeneyl-G were synthesized enantioselectively starting from (R)-carvone. Both show potent and selective anti-herpesvirus activity (HSV-1, HSV-2, VZV, CMV). Molecular modeling demonstrates that both isomers are bound in the active site of HSV-1 thymidine kinase in a high-energy conformation with the base moiety orienting in an equatorial position. It is believed that the flexibility of the cyclohexene ring is essential for their antiviral activity. 相似文献
367.
Lata R Conway JF Cheng N Duda RL Hendrix RW Wikoff WR Johnson JE Tsuruta H Steven AC 《Cell》2000,100(2):253-263
Typical of DNA bacteriophages and herpesviruses, HK97 assembles in two stages: polymerization and maturation. First, capsid protein polymerizes into closed shells; then, these precursors mature into larger, stabler particles. Maturation is initiated by proteolysis, producing a metastable particle primed for expansion-the major structural transition. We induced expansion in vitro by acidic pH and monitored the resulting changes by time-resolved X-ray diffraction and cryo-electron microscopy. The transition, which is not synchronized over the population, proceeds in a series of stochastically triggered subtransitions. Three distinct intermediates were identified, which are comparable to transitional states in protein folding. The intermediates' structures reveal the molecular events occurring during expansion. Integrated into a movie (see Dynamic Visualization below), they show capsid maturation as a dynamic process. 相似文献
368.
Hendrix LR 《FEMS microbiology letters》2000,192(1):119-124
Although Bartonella bacilliformis causes a severe anemia in humans, this study presents the first report of hemolytic activity by B. bacilliformis. The activity was not apparent in culture supernatants but was reliably detected when B. bacilliformis cells were centrifuged onto erythrocytes prior to incubation. Abrogation of hemolytic activity by proteinase K treatment suggested the hemolysin was a Bartonella protein. Even though hemolysis required relatively long incubation times, de novo protein synthesis was not required to produce the protein. A preparation containing factors released by B. bacilliformis, including deformin, a B. bacilliformis protein able to induce pits and invaginations in erythrocyte membranes, had some ability to lyse erythrocytes. However, pre-deformed erythrocytes did not lyse faster or to a greater extent than control erythrocytes after the addition of B. bacilliformis cells. Inhibition of deformation caused by B. bacilliformis cells with the erythrocyte ATPase inhibitor, vanadate, did not affect hemolytic activity. This study suggests hemolytic activity and deforming activity are attributable to different B. bacilliformis proteins. 相似文献
369.
370.
Mediavilla J Jain S Kriakov J Ford ME Duda RL Jacobs WR Hendrix RW Hatfull GF 《Molecular microbiology》2000,38(5):955-970
Mycobacteriophage Bxb1 is a temperate phage of Mycobacterium smegmatis. The morphology of Bxb1 particles is similar to that of mycobacteriophages L5 and D29, although Bxb1 differs from these phages in other respects. First, it is heteroimmune with L5 and efficiently forms plaques on an L5 lysogen. Secondly, it has a different host range and fails to infect slow-growing mycobacteria, using a receptor system that is apparently different from that of L5 and D29. Thirdly, it is the first mycobacteriophage to be described that forms a large prominent halo around plaques on a lawn of M. smegmatis. The sequence of the Bxb1 genome shows that it possesses a similar overall organization to the genomes of L5 and D29 and shares weak but detectable DNA sequence similarity to these phages within the structural genes. However, Bxb1 uses a different system of integration and excision, a repressor with different specificity to that of L5 and encodes a large number of novel gene products including several with enzymatic functions that could degrade or modify the mycobacterial cell wall. 相似文献